The Effect of Varying Weightload Intensities on Biceps Curl Technique

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1 Western Michigan University ScholarWorks at WMU Master's Theses Graduate College The Effect of Varying Weightload Intensities on Biceps Curl Technique Jeffrey C. Gailhouse Western Michigan University Follow this and additional works at: Part of the Health and Physical Education Commons, and the Rehabilitation and Therapy Commons Recommended Citation Gailhouse, Jeffrey C., "The Effect of Varying Weightload Intensities on Biceps Curl Technique" (1992). Master's Theses This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact

2 THE EFFECT OF VARYING WEIGHTLOAD INTENSITIES O N BICEPS CURL TECHNIQUE by Jeffrey C. Gailhouse A Thesis Submitted to the Faculty of The G raduate College In partial fulfillment of the requirements for the D egree of Master of Arts D epartm ent of Health, Physical Education, a n d Recreation Western M ichigan University Kalam azoo, M ichigan D ecem b e r 1992

3 THE EFFECT OF VARYING WEIGHTLOAD INTENSITIES ON BICEPS CURL TECHNIQUE Jeffrey C. Gailhouse, M.A. Western M ichigan University, 1992 This study described biom echanical deviations from proper biceps curl technique specifically in the shoulder, trunk, body a n d knee angles, th a t occurred in response to varying intensities of an individual's 1 RM (repetition maximum). Ten college a g e males participated in the study. Subjects w ere required to perform one repetition a t 60%, 70%, 80%, 90% and 100% of his 1 RM. The only differentiating facto r was the order in which the five intensities w ere perform ed. Condition order was random ized to minimize bias. M ovem en t was filmed with a high-speed motion picture c a m e ra, digitized a n d then analyzed with com puter software. The findings indicated that a relationship existed b etw e en resistance and the m agnitude of m ovem ent in the selected angles. As resistance increased, angular m o vem en t correspondingly increased. It was concluded that training a t intensities less than 90% of an individual's 1 RM was more conducive to proper technique a n d would still allow for optim al strength gains.

4 ACKNOWLEDGMENTS I would like to express my sincere appreciation to my advisors Dr. M ary Dawson a n d Dr. Roger Zabik. The personal Interest that they took in my professional training over the past six years has strongly prepared m e for a career in which I can educate individuals on the im portance of maintaining personal fitness. I will be eternally grateful for their g uidance and support. I would also like to thank Dr. Bob Moss for taking th e time to serve as a com m ittee m em ber. His preciseness and attention to detail helped to provide a wellwritten manuscript. Jennifer Hadfield, a colleague and a close friend, is also deserving of special thanks. She was very helpful during the d a ta collection phase of this project. Her encouragem ent and support w ere greatly appreciated. Kathy Wittliff was instrumental in perfecting the cosm etic a p p e a ra n c e of the final draft. Her com puter expertise alleviated the burden of form at specifications, which allow ed m e to concentrate on the composition of the manuscript. She generously d o n ated her tim e a n d deserves my heartfelt thanks. Finally, I would like to thank my wife Pat, whose prompting a n d support helped m e to persevere during the final stages of this project. I cannot possibly begin to thank her for her p atie n ce during th e years it took m e to obtain my graduate degree. Jeffrey C. Gailhouse

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7 O rder N um ber The effect of varying weightload intensities on biceps curl technique Gailhouse, Jeffrey Charles, M.A. Western Michigan University, 1992 UMI 300 N. Zeeb Rd. Ann Arbor, M I 48106

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9 TABLE OF CONTENTS ACKNOW LEDGEMENTS... LIST OF TABLES... LIST OF FIGURES... ii vl vii CHAPTER I. INTRODUCTION... 1 Statem ent of the Problem... 1 Purpose of the Study... 1 D elim itations... 2 Lim itations... 2 Assumptions... 2 Definition of Terms... 3 II. REVIEW OF LITERATURE... 5 Biom echanical Im p lic a tio n s... 6 M ech an ic s-l evers... 6 C enter of Gravity... 7 Strength Training G u id e lin e s... 7 P rinciples... 7 Program V a ria b le s... 8 Strength Training Programs... 9 Technique Im plications Proper Technique Training Related Injuries... 13

10 Table of C ontents-c ontinued CHAPTER Biceps Curl T e c h n iq u e III. DESIGN AND METHODOLOGY Subject Selection Instrum entation Photo-Sonic 1PL C am e ra V anguard Motion A n a ly z e r Peripheral Instrum entation Experimental Procedures D a ta Analysis Statistical P ro c e d u re s IV. RESULTS AND DISCUSSION Results H om ogeneity of V a ria n c e Shoulder Angle Trunk A n g l e Body A n g l e Knee A n g l e Discussion Shoulder Angle Trunk A n g l e Body A n g l e Knee A n g l e R elated F a c to rs iv

11 Table of C ontents-c ontinued CHAPTER V. SUMMARY. FINDINGS, CONCLUSIONS, AND RECOM M ENDA TIO NS APPENDICES S u m m ary Findings Conclusions R e c o m m e n d a tio n s...47 A. Hum an Subjects Review Board A c c e p ta n c e F o r m B. Informed Consent C. Subject-Treatment O r d e r D. A natom ical Landmarks for Joint Angle Calculation E. Subject Raw Angle D a t a F. Group M eans by Joint A n g le BIBLIOGRAPHY V

12 LIST OF TABLES 1. Summary Table for Hom ogeneity of Variance vi

13 LIST OF FIGURES 1... Subject 7 Shoulder Angle M ovem ent P a tte r n Subject 2 Shoulder Angle M ovem ent P a tte r n Subject 3 Shoulder Angle M ovem ent P a tte r n Subject 2 Trunk Angle M ovem ent P a tte rn Subject 9 Trunk Angle M ovem ent P a tte r n Subject 7 Trunk Angle M ovem ent P a tte r n Subject 5 Trunk Angle M ovem ent P a tte r n Subject 7 Body Angle M ovem ent P a tte r n Subject 6 Body Angle M ovem ent P a tte r n Subject 1 Body Angle M ovem ent P a tte r n Subject 9 Body Angle M ovem ent P a tte r n vii

14 CHAPTER I INTRODUCTION A great d eal of confusion and dissension exists am ong professionals in the field of sport pertaining to w eight training principles. This dilem m a is quite evident in the a re a of strength training. Strength trainers are divided over the issue of training intensities. Some trainers maintain that higher training intensities, a t the expense of proper technique and form, produce optimal gains in terms of strength developm ent. Others, however, feel that training a t a slightly lower intensity level emphasizing proper technique will yield optim al results. Research to determ ine the effects that various training intensities have on proper technique is for the most part, nonexistent. Even though strength gains are to b e e xp ected with most training intensities, an optimal training zone must be established through research to maximize the potential benefits of resistance training. Statem ent of the Problem The problem in this study was to determ ine, in the sagittal plane, deviations that occur as a result of varying intensities in relation to the one repetition maximum (1 RM). M ore specifically, varying intensities m ay elicit a variety of biom echanical movements th a t are incorrect with regard to proper technique. Purpose of the Study With naked eye observation it c an be ascertained that high intensity resistances cause a g reater d e g re e of technique deviation than lighter intensities. For 1

15 exam ple, an individual performing a biceps curl a t 90% of 1 RM will dem onstrate a m arked difference in technique w hen com pared to a curl a t 60% of 1 RM, Studies to determ ine the m agnitude of differences in terms of biom echanical technique am ong different training intensities w e re not found in the literature. In order to obtain the most benefit from a strength training program, an individual must train a t optimal intensity levels. Studies investigating the biom echanical changes that occur during the execution of the biceps curl n eed to be con d u cted to facilitate the establishment of optim al training intensities. Delimitations The study was delim ited to the following characteristics: 1. Participants w ere b etw e en the ages of 19 and 23 years. 2. Subjects w ere males currently enrolled a t Western M ichigan University. 3. N one of the subjects received instruction about maintaining proper tech niqu e prior to testing. 4. M ovem en t was only filmed in the sagittal plane. Limitations A limitation of this investigation was that subjects w ere random ly selected from respondents to verbal announcem ents m a d e in general physical education weight training classes. Consequently, most of the subjects h ad prior w eight training experience. The presence of these characteristics m ay limit the application of results to other populations. Assumptions The study was c o n d u cte d under the following assumptions:

16 1. The participants perform ed consistently with m axim al effort on all trials so that true anatom ical m echanics could be recorded. 2. The instrumentation used for d a ta collection a n d analysis was a ccurate and reliable. Definition of Terms The following terms a n d definitions are pertinent to th e understanding of this study: 1. Antagonistic muscle--the muscle that produces the opposite joint action to that of the prime mover muscle. 2. Concentric contraction-m uscular contraction in which the muscle exerts force a n d shortens. 3. Eccentric contraction-m uscular contraction in which the muscle exerts force and lengthens. 4. Intensity--the p ercenta g e of w eight lifted in relation to the 1 RM. 5. Joint extension-increasing the angle b etw e en tw o a d ja c e n t segments. 6. Joint flexion-decreasing the angle betw een two a d ja c e n t segments. 7. O ne repetition m axim um (1 R M )-th e maximum am ount of w eight lifted one tim e with correct form for a specific exercise. 8. Prime m over m uscle-the muscle that contracts to accom plish the desired m ovem ent. 9. Range of motion (R O M )-fo r the biceps curl a m ovem ent from a position of full extension to a position of full flexion. 10. R epetition-m oving a w eightload from a position of full extension to a position of full flexion and b ac k to th e initial position of full extension. 11. Treatm en t-th e specific resistance a t which e a c h subject was tested.

17 12. Trunk Inclination-m ovem ent of the upper body torso, either forward or b ackw ard, from a normally e rect position. 13. W eightload--the am ount of resistance, expressed in pounds, with which an individual exercises.

18 CHAPTER II REVIEW OF LITERATURE The biceps brachli a n d brachialis are the elbow flexors. W hen the upper arms a n d elbows remain in a fixed position, the elbow flexors serve as the prime m over muscle group which results In a more beneficial training effect. For this reason, the biceps curl must be perform ed with very strict technique. Very few, if any, studies have been c onducted concerning the biom echanical changes that occur as the biceps curl is executed. Additionally, no research has b een done on the effects that vaiying w eightload intensities have on biceps curl technique. In order to accurately analyze a n individual's lifting technique a n d to establish programs implementing optimal training intensities with proper technique, an understanding of the fundam entals of strength training is necessary. Knowledge of weight training principles, variables, and programs is essential. Equally im portant is an understanding of how proper technique influences the outcom es of a weight training program and aids in injury prevention. The implications that the field of biom echanics has on strength training also merit consideration. Thus, an a c c u ra te biom echanical analysis of the biceps curl can only b e m a d e with background knowledge in the fields of strength training and biom echanics. This c h a p te r is organized into three sections: (1) biom echanical implications, (2) strength training guidelines, a n d (3) technique implications. 5

19 Biom echanical Implications Mechanics--Levers The effectiveness that w eight training has on improving strength is influenced by the anatom ical arrangem ents of limbs, joints and muscles. An understanding of how these body parts interact to form a system of levers helps strength coaches design m ore effective training programs. A lever system is comprised of three components: a fulcrum (joint), a resistance (weight), and a force (muscle contraction). Within the body there are three classes of levers. Each class of lever serves a specific purpose in the body. In a Class I lever system the fulcrum is located betw een the resistance and th e force. Class I lever systems are responsible for maintaining equilibrium. A teetertotter is an exam ple of a Class I lever. Individuals on e a c h end of the teeter-totter serve as the resistance and the force, both acting dow nw ard, with the fulcrum located b etw e en them. The resistance is located betw een the fulcrum and the force in a Class II lever system. This type of lever system serves to conserve energy by reducing the am ount of force necessary to accom plish the desired m ovem ent. An exam ple of a Class II lever system is a w heel barrow. The axle serves as the fulcrum, the w eight in the bucket serves as the resistance, and the force is applied by the individual lifting up on the handles. In a Class III lever system the force is situated betw een the fulcrum and the resistance. This lever system is responsible for speed a n d range of m ovem ent. Performing the biceps curl Is an exam ple of a Class III lever system. The force Is the contraction of the biceps muscle, the elbow serves as the fulcrum, and the weight being held in the hand serves as the resistance. With increased resistance, the biceps must exert greater force in order to accomplish the desired m ovem ent throughout the range of motion.

20 C enter of Gravity The am ount of force a muscle must exert is Influenced by its position in relation to the body's center of gravity. The weight of a body acts vertically dow nw ard through its center of gravity, establishing a line of action (Watkins, 1983). This can be illustrated by drawing a vertical line through the center of a body's profile view. This line of action is a key facto r in terms of body stability. Watkins (1983) stated that a body is most stable w hen its line of action falls within its base of support. During the execution of the biceps curl th e body's center of gravity changes In relation to the line of action and stability is m aintained through body m ovem ent. W hen an individual performs a strength exercise against a correct resistance needless body m ovem ent will b e minimized. A joint's position in relation to the body's line of action also influences the am ount of force a muscle must exert to accomplish a desired m ovem ent. The g reater the distance betw een a joint and the line of action, the greater the force required from the muscles involved with joint m ovem ent. W hen m ovem ent about the shoulder joint during the biceps curl is kept to a minimum the role of the elbow flexors as the prime movers of the elbow joint is emphasized. Training a t an optim al intensity level, from a biom echanical perspective, will allow the individual to maintain proper tech niqu e a n d experience m axim al strength gains. Strength Training Guidelines Principles The goal of strength training programs is to elicit increases in muscular strength a n d /o r muscular endurance. Muscular strength is the ability of a muscle to contract against a resistance. The ability of a muscle to m ake re p e a te d contractions Is muscular endurance. Muscular strength a n d muscular en d u ran ce are interrelated in

21 th a t an increase in one com ponent will generally result in a n Increase In the other com ponent. Three basic principles must be im plem ented to derive maximum gains from strength training programs. First, muscular adaptations only occur w hen the muscles are overloaded--forced to contract against near maximum resistances. This principle has been term ed the overload principle. Second, muscles a d a p t to the load they are subjected to, therefore it is necessary to continually overload the muscle in order to prom ote further strength gains. As strength increases from training, so must the am ount of resistance that an Individual exercises against. If the resistance is not increased, the existing strength level will be m aintained, not improved. Therefore, the intensity in terms of the resistance must be progressively increased to prom ote further strength gains, a principle known as progressive resistance. Third, the principle of specificity implies that muscle adaptations are specific to the type of training that is perform ed. If a muscle is e n g a g e d in endurance type exercises, the endurance c a p a c ity of a muscle is increased. If a muscle is e n g a g e d in heavy resistance training, muscular strength is increased. The inclusion of these principles into a training program will allow the individual to maximize strength gains. Program Variables Strength training programs are organized into repetitions (the num ber of times th a t a w eight is lifted) a n d sets (a sequence of repetitions). An optim al com bination of sets and repetitions to achieve optim al strength gains has not b een established. The most successful programs im plem ent a range of 6 to 12 repetitions per set with a minimum of three sets. Strength programs are based upon the am ount of w eight that c a n be lifted for a selected num ber of repetitions before fatigue sets in. This resistance has b e e n term ed the repetitions maximum. Most strength training programs a d v o c a te exercising with a w eight that c a n b e lifted ten times in succession; the ten repetitions

22 maxim um, or 10 RM. O nce th e 10 RM can be perform ed for all sets, the w eightload should be increased. As the resistance Increases, strength correspondingly Increases. The w eightload and num ber of repetitions and sets within a program c an be m anipulated to m eet the goals of the individual. For optim al gains In muscular strength, more sets with few er repetitions are perform ed against a heavier resistance. For exam ple, the 7 RM perform ed against 90% of the 1 Rm for five sets might be executed. Muscular endurance is improved w hen more repetitions are performed against a lighter resistance. A muscular endurance protocol might require 4 sets of the 10 RM to be perform ed against 70% of the 1 RM. Regardless of the desired outcom es of a strength training program, the resistance must be progressively increased as the individual is able to successfully com plete the desired num ber of sets a n d repetitions so that th e muscle is consistently overloaded. Strength Training Programs Three types of strength training programs are used to elicit strength gains; Isometric, isokinetic, a n d isotonic. Each m odality has advan tag es as well as limitations. Isometric training involves a static muscle contraction in which the length of the muscle remains constant (does not shorten or lengthen) when force is exerted against a fixed resistance. Isometric exercises are usually perform ed against a stationary resistance such as a wall or a training partner. The results of a study that involved the execution of a daily maximum isometric contraction for a one second duration dem onstrated a 5% weekly increase, over an eight w eek tim e period, in strength over initial strength levels (Hettinger & Muller, 1953). Despite the improvements in strength, isometric training has severe limitations. Progress, In terms of strength developm ent, is difficult to evaluate (M cardle, Katch, & Katch, 1986). The absence of identifiable measures of resistance (w eight) makes it difficult to chart Im provem ent. Isometric

23 exercises do not involve limb m ovem ent, therefore muscle activation and subsequent strength gains are specific to the joint angle a t which contraction occurred (Lindl, 1979; Zabik, 1967), In order for isometric training to be overtly beneficial several angles throughout the range of motion must be exercised for e a c h respective muscle group. The tlm e-to-benefit ratio is less than desirable and therefore this form of training is frequently ignored. Isokinetic strength training is an outgrowth of Isotonic training. This form of training requires muscular contraction to occur a t a constant velocity (Powers & Howley, 1990). As the length of the muscle changes, the resistance varies proportionally to m atch the force exerted by the muscle. Isokinetic machines allow th e exerciser to exert maximal force throughout the entire range of motion. This Is accom plished by com bining variable resistance capabilities with a speed governing feature. Exercisers select a speed a t which they desire to exercise; maximal effort is required w hen the exerciser's rate of m ovem ent m atches th e selected speed. The speed governing feature allows for smooth and controlled muscle contraction. Injuries on isokinetic machines are very rare because of this controlled speed of m ovem ent. The fundam ental basis of isokinetic training is appealing, but several disadvantages prevent Its w idespread use in public fitness facilities (Foran, 1985). On some types of isokinetic machines there is no resistance during the eccentric phase of the repetition. Foran (1985) indicated that optim al strength gains occur w hen muscle is forced to exert resistance during the eccentric as well as the concentric phase of contraction. Isokinetic m achines govern the speed of m ovem ent rather than the am ount of resistance, which allows the individual to "cheat" in the sense that muscular exertion c an range from minimal to maximal. A great d eal of tim e Is required to chonge ond adjust these machines for e a c h different body part. Isokinetic m achines inhibit the body's ability to develo p b a la n c e d u e to the fixed path o f m ovem ent. Only prime

24 m over muscles are stressed, with no assistance from agonist muscle groups. Due to the cost a n d com plexity of these machines, they are usually found in rehabilitation facilities (Shankm an, 1984). Isotonic strength training involves concentric as well as eccentric muscle contraction. Exercises are typically perform ed with variable resistance machines or free weights. Variable resistance training provides a resistance that fluctuates so that it m atches a joint's ability to produce force throughout the range of motion (W eltm an & Stamford, 1982). Equipment, via the use of a c a m or lever system, provides greater resistance a t the joint angles at which the individual is stronger and a lesser resistance a t the w eaker angles, therefore accom m odating the lifter's strength. Variable resistance machines incorporate both concentric and eccentric muscle contraction. It is easy to evaluate progress because the lifter can increase the resistance, sets, or num ber of repetitions. Changing the w eight is accom plished by simply moving a pin up and dow n the stack of weights. The machines are very safe to use because the weights m ove in a fixed path a n d for m any exercises, a spotter is not necessary. As with other forms of strength training, variable resistance has its disadvantages. The resistance changes that occur throughout the range of motion are based upon averages of force-angle curves (Foran, 1985). Human beings vary in terms of limb length, therefore limiting the application of these force-angle curves in the design of variable resistance equipm ent. Exercises occur in a fixed path, which prevents assisting m ovem ent from agonist muscles and hinders the developm ent of muscular coordination (balance). Finally, the machines themselves a re very expensive and require a great d eal of m aintenance. Free weight training involves muscular contraction against a constant resistance. Training with free weights requires the activation and coordination of antagonist in addition to prime m over muscle groups (Foran, 1985). There is not a fixed

25 path of m ovem ent with free weights, which allows the exerciser to develop a sense of balan ce. As noted earlier, this form of strength training employs both concentric and eccentric contraction; research indicates that this com bination results in more significant strength gains w hen com pared to training either separately (Foran, 1985). Strength gains are easy to monitor, as evidenced by increases in weightloads, sets, or repetitions. Changing weights is very quick and easy to do. Free w eight equipm ent is relatively inexpensive and requires minimum m aintenance. Despite advantages, the use of free weights does have inherent limitations. When exercising against constant resistance, the muscle is only as strong as its weakest point throughout the range of motion. This deficiency is com pounded when the individual employs improper technique to accom plish the desired movements. More importantly, free weight use is a cc o m p a n ie d by a n increased c h a n c e of injury. Some form of injury is almost certain to occu r if proper tech niqu e and safety procedures are not observed. Technique Implications Proper Technique Mastery of the proper techniques for strength training exercises is an absolute prerequisite for improving muscular strength and avoiding injury. For maxim al benefit, all repetitions should be perform ed slowly throughout the full range of motion (Stamford, 1984). Controlling th e weight, as opposed to swinging or dropping it, places maxim al stress on the exercising muscle groups. Im proper technique allows for assisting m ovem ent from agonist muscle groups, therefore reducing the am ount of stress p la ced on prime mover muscle groups. Performing strength exercises against too heavy of a resistance results in poor technique. During certain phases of concentric contraction, m om entum, c re a te d by body motion, assists in m ovem ent of the

26 resistance rather than by th e muscles exclusively. Pausing a t full extension a n d full flexion, along with slow controlled m ovem ent reduces the risk of sustaining a n injury. Training R elated Injuries Strength training programs, in an a ttem p t to reduce th e c h a n ce of injury during athletic participation, have on numerous occasions been the cause of an injury. The presence of this dilem m a might cause some individuals to question the legitim acy of strength programs as a m eans of injury prevention. Studies indicate that strength training Injuries are the result of one or more factors. These causal factors have been identified as a lack of professional (qualified) supervision, improper technique, and overuse (Shankman, 1984). Furthermore, it has b een suggested that the type of injury sustained m ay b e related to the typ e of training program th a t is used. Isometric training, as noted earlier, involves muscular contraction with no c h a n g e in the!o!nt angle. Injuries are nearly nonexistent in well-designed and supervised isom etric programs. Injuries that occur are in the form of muscular strains th a t are a result of a sudden a n d maximal contraction (Shankman, 1984). The prevention of these strains is contingent upon performing slow and controlled contractions in which tension is gradually increased, rather than occurring instantaneously. Despite the relative safety of isometric strength training, it is very ineffective in terms of optim al strength developm ent. It was stated earlier in this section that isokinetic strength training is perform ed on m achines that com bine accom m o datin g resistance with a speed governing capability. Shankman (1984) cited improper technique as th e cause of muscle injury on isokinetic machines. Explosive muscle contraction against slow speed, high resistance settings places a trem endous am ount of stress on the exercising joint and con n ective tissue. The key to injury prevention on Isokinetic m achines is the sam e as

27 th a t of any other training protocol, slow a n d controlled m ovem ent throughout the entire range of motion. Isotonic (variable resistance and free w eight) modalities are the most popular, and unfortunately, the most dangerous forms of strength training. The num ber and severity of injuries sustained on isotonic equipm ent by far outnumbers other training protocols. Isotonic injuries are a result of uncontrolled eccentric m ovem ent and explosive concentric contraction against too heavy of a resistance. In addition to strain, joints and surrounding structures are subjected to excessive torque, compression and shear forces (Shankman, 1984). The bottom line to injury prevention in strength training programs is proper technique. Qualified supervision, a gradual increase in w eightload, and com plete adh eren ce to proper lifting technique will facilitate maximal strength gains. Biceps Curl Technique A great d eal of literature has been published on the m echanics of the biceps curl technique, but nothing with regard to technique deviation as a result o f increased weightloads. A review of literature revealed that a consensus existed concerning proper biceps curl technique (Hesson, 1985; Kostik & Knortz, 1980; McKeon, 1990; Rasch, 1990; Riley, 1983; Schwarzenegger, 1985; W escott, 1982). For this reason, only one author's view was included to describe the proper technique of the biceps curl. The literature suggested that the barbell curl is one of the most popular exercises for the biceps muscle group. Two points of emphasis w ere prevalent in the literature. W escott (1982) stressed th a t the key to obtaining desired results from the exercise was contingent upon the ability of the upper arms to remain stationary while the lower arms w ent through the full range of motion. He em phasized that m ovem ent must occur at th e elb ow joint, with a minimum of assisting m ovem ent a t the shoulder joint. W escott

28 stated th a t w hen the upper arms w ere kept stationary and the elbows w ere pressed Into the sides, the ensuing curling m ovem ent was a result of biceps activation. O f equ al im portance in the literature was trunk m ovem ent. Wescott stressed the im portance of maintaining a n erect trunk during the execution of the barbell curl. Trunk m ovem ent, w hether forward or backw ard, reduced the role of the biceps as the prime m over muscle group a n d allow ed other body segments to assist in the m ovem ent. Additionally, trunk m ovem ent resulted in an increase in m om entum as the w eight was curled upward a n d further reduced the role of the biceps in the exercise. An interpretation, based upon a review of multiple sources, resulted in the following depiction of a proper biceps curl. M ovem ent started with the arms in a fully extended position. As the w eight was curled upward to a position of full flexion, the position of th e elbows rem ained u nchanged (tucked into the sides) and the trunk rem ained erect, having p la c e d all of the stress on the biceps muscle groups. The repetition was c o m pleted by slowly lowering the weight back to the starting position.

29 CHAPTER III DESIGN AND METHODOLOGY The purpose of this study was to Identify the deviations in proper biceps curl technique th a t occur as a result of the varying intensities of an individual's 1 RM. The c h a p te r is organized into four content areas: (1) subject selection, (2) instrumentation, (3) experim ental design, (4) d a ta analysis a n d (5) statistical procedures. Subject Selection Subjects that participated in this study w ere ten m ale college students b etw een th e ages of 19 and 23 years. During the d a ta collection phase of the investigation, the participants w ere enrolled in general physical education w eight training courses. Prior to testing, announcem ents regarding the study w ere m a d e to various sections of w eight training classes and interested students c o n ta c te d the researcher. The subjects th a t com prised the data-producing sample w ere then randomly selected from the general population of respondents. The study was app ro ved by the Human Subjects Review Board a t Western M ichigan University. The approval form is presented in Appendix A. Prior to d a ta collection, the subjects w ere questioned with respect to their health status. Each of th e subjects indicated that there w ere no health risks present th a t would prevent them from performing the testing procedure. A consent form was signed and d a te d by e a c h subject. Appendix B contains a cop y of the consent form. 16

30 Instrumentation Several pieces of blom echanlcal instrumentation w ere necessary to ensure a c c u ra te d a ta collection a n d valid analysis. The Instruments that w ere used in this study have been used repeatedly in other studies th a t involved m ovem ent analysis. Photo-Sonic 1PL C am era The filming was done with a Photo-Sonic 1PL cam era. This high speed 16 mm c am e ra was specifically designed to film rapid m ovem ent events. The fram e rate for this c a m e ra ranges b etw e en 10 and 500 pictures per second. The d eveloped film allows the view er to perform a fram e-by-fram e analysis of the m ovem ent. This instrument was calibrated prior to filming, to ensure a reliable and a ccurate m ethod of d a ta collection. The calibration procedure of the cam e ra centered around correct film speed. The accuracy of th e selected film speed was contingent upon tw o factors. Prior to filming the cam era's p ow er pack was fully charged. In addition, light emitting diodes (LED's) w ere exposed on the film during filming. The LED's w ere used as a m ethod of calibrating film speed. V anguard Motion Analyzer The film analysis phase of the project required the use of a Vanguard motion analyzer, serial num ber 23752, equipped with projection h e a d M -16C. The motion analyzer is designed so th a t a fram e-by-fram e analysis of the m ovem ent pattern can b e m ade. Peripheral Instrumentation Additional Instrumentation was necessary for film analysis. The film digitizing process

31 was com pleted with a Numonics Electronic Graphics calculator that was interfaced with a com puter. D ata analysis was done with the use of Peak 3-D software, version 4.5 (Peak Perform ance Technology IES, Inc., 1989). Before the digitizing process b egan, a reference measure filmed prior to the treatm ent procedures, was identified and true vertical and horizontal measures w ere established so that the Input d a ta would be accurate. To provide a d e q u a te lighting, six banks of Colortron lights w ere used during filming. The use of these lights elim inated shadows, which m a d e it easier to d e te c t joint m ovem ent during film analysis. Experimental Procedures All d a ta w ere c o llected in one afternoon. To test th e research problem that varying intensities of the 1 RM elicit biom echanical movements that are incorrect with regard to proper biceps curl technique, a rep eated measures design was im plem ented. A random ized order of testing was incorporated in this design, which allow ed for more valid d a ta production. The subjects perform ed e a c h of the five conditions in a random order. The selected conditions for this study w ere 60% (Condition 1), 70% (Condition 2), 80% (Condition 3), 90% (Condition 4), and 100% (Condition 5) of e a c h individual's 1 RM. The subjects w ere film ed with the Photo-Sonic 1PL c a m e ra set a t a speed of 100 fps (feet per second) from a distance of approxim ately 25 feet. For this particular study, only the concentric phase of e a c h condition was filmed. The subjects w ere all film ed with th e right side of their body facing the cam era. The filming of the subjects was done against a black background to help facilitate the viewing of body m ovem ent during film analysis. Six banks of Colortron lights w ere aim ed directly a t the subjects to provide a d e q u a te lighting for filming. Prior to filming, a reference measure, a yardstick, was filmed for analysis purposes. Every subject perform ed a com plete

32 repetition a t e a c h of five pre-determ ined intensities. For e a c h of the repetitions, subjects initiated m ovem ent upon reception of a verbal com m and from the cam era operator. At the com pletion of e a c h repetition the necessary w eightload adjustments w ere m a d e a n d the procedure was repeated. The film analysis took p la ce in Western Michigan University's biomechanics laboratory. The film was lo a d e d into the Vanguard motion analyzer and projected dow n on a white table. Before film digitizing b eg an, the reference measure, taken prior to the testing procedure during filming, was located and a scale factor for fram e analysis was set. Each condition for every subject was view ed in its entirety and key frames for the digitizing process were selected. Each selected fram e was projected on the ta b le and 13 anatom ical landmarks w ere plotted on a n X-Y coordinate graph, The landmarks representing joint centers that w ere plotted consisted of th e following: ( I ) distal point of the right hand, (2) right ulna styloid, (3) right cen ter of elbow, (4) right coracoid process, (5) distal point of the right foot, (6) right m edial malleolus, (7) right center of knee, (8) right greater trochanter, (9) top of sternal notch, (10) pubic bone, ( I I ) tragus of the ear, (12) to p of head, and (13) center of object. O n c e e a c h landm ark was located, the X-Y coordinate was entered with the Numonics Electronic Graphics calculator and the d a ta w ere entered into the interfaced com puter. This process was re p eated for all of the selected frames. At the conclusion of e a c h treatm ent, the subject's weight, the object's w eight and the time b etw e en frames was entered and the d a ta w ere stored. D ata Analysis D a ta analysis was c o m pleted by using a re p eate d measures design. The d e p e n d e n t variable was defined as the range of motion in th e sagittal plane during th e various phases of the biceps curl. The independent variables w ere defined as the

33 different w eightload intensities of an individual's 1 RM: 60%, 70%, 80%, 90%, and 100%. Each subject perform ed th e conditions in a random order. For exam ple, Subject 1 m ay have perform ed Condition 4 first, while Subject 2 m ay have perform ed Condition 1 first. Presenting the conditions in a random order provided internal validity (the d e g re e to which the independent variable caused change in the d ep e n d e n t variable) for th e study. M ore specifically, error such as testing effect, was minimized in the study. A ppendix C contains a listing of the order in which e a c h subject perform ed the conditions. D a ta comparisons am ong subjects w ere m a d e to determ ine the m agnitude of differences with respect to body m echanics that occurred for e a c h condition. Of particular interest w ere the angular changes that occurred a t the shoulder, trunk, body, a n d knee joints. In order to calculate the angle for a specific joint, it was necessary to use the X-Y coordinate values of three anatom ical locations. PI and P2 w ere the segm ental endpoints of a particular angle and V (vertex) was the point of intersection of the tw o sides of the angle. Appendix D contains a listing of the anatom ical landmarks that w ere used for the calculation of e a c h joint angle. The shoulder angle was calculated with the X-Y coordinate values of the right elbow (P I), the right shoulder (V) a n d the horizontal (P2). The body angle was calculated with the X-Y coordinate values of the right shoulder (P I), the right ankle (V), a n d the vertical (P2). The X-Y coordinate values of the right wrist (P I), the right elbow (V), and the right shoulder (P2), w ere used to calculate the elbow angle. The trunk angle was calc u late d with the X-Y coordinate values of the right shoulder (P I), the right hip (V), a n d the vertical (P2). The X-Y coordinate values of the right hip (P I), the right knee (V), a n d the right ankle (P2) w e re used to c alcu late the knee angle. The angular position of the elbow during the execution of the biceps curl was used as a reference measure to select key frames for analysis a n d comparison. Five

34 positions w ere selected to analyze biom echanical deviations th a t occurred in response to the various conditions. The first position selected was the actual initiation of the biceps curl. The second position selected for analysis was a t 135 elbow flexion. An elbow angle of 90 was selected as the third position for d a ta analysis. The fourth position was a t 45 elbow flexion. The final position selected for analysis was at the com pletion of all body m ovem ent. The initiation and com pletion positions were necessary in order to determ ine the m agnitude of change that occurred at selected joints during the execution of the biceps curl. The position of 90 elbow flexion was selected because it has been referred to as the "sticking point" during the repetition. In other words, it is a t this position that the body deviates in order to facilitate m ovem ent. The positions of 135 and 45 elbow flexion were selected because they hypothetically fall h a lfw a y b etw e en 90 and their respective initiation and com pletion positions. Statistical Procedures Several statistical procedures w ere used to describe th e d a ta that was g e n e ra te d in the study. The m e an of the group for e a c h of the selected angles was used to com pare the differences am ong the five conditions. Descriptive statistics were used to describe patterns of motion for each joint angle. F-ratios w ere used to determ ine variability betw een the conditions. The independent variables were: (a) the five conditions, 60%, 70%, 80%, 90% and 100% of the subject's 1 RM; and (b) the random ized treatm ent order of the five conditions. The d ep e n d e n t variables that w ere m easured w ere changes in: (a ) shoulder angle, (b) trunk angle, (c) body angle, and (d) knee angle.

35 CHAPTER IV RESULTS AND DISCUSSION This c h apter summarizes the results obtained from the present study and discusses th e implications of th e results in identifying an optim al training intensity for the biceps curl. The purpose of this study was to identify the biom echanical deviations th a t occurred in response to increased w eightload intensities, thereby making it possible to identify an optim al training intensity for the biceps curl. It was the intention o f this p a p e r to help alleviate some of the confusion surrounding training intensities in th e field of strength training by providing biom echanical evidence that supports the contention that a specific training intensity will facilitate proper strength training technique a n d yield m axim al gains in terms of strength im provem ent. The following raw d a ta w ere used to analyze the biom echanical deviations th a t resulted from increased w eightload intensities: (a) shoulder angle, (b) trunk angle, (c ) body angle, and (d) knee angle. The g en erated d a ta w ere analyzed on an individual and group basis. For every subject, comparisons w ere m a d e am ong conditions to identify significant changes in the selected anatom ical parameters. Comparisons am ong conditions with respect to the group of subjects as a whole w ere m a d e by calculating the m ean, the variance, and the F-ratio from the raw d a ta. The descriptive d a ta of e a c h subject for all five conditions are presented in Appendix E. Results For descriptive analysis purposes the motion of the arm curl was divided into four phases. Phase I b e g a n with the initiation of the curl and e n d e d w hen the elbow 22

36 re ached 135. Phase II b e g a n w hen the elbow angle was 135 a n d ended w hen the elbow re ached 90. Phase III b eg a n w hen the elbow angle was 90 a n d e nded when th e elbow re ached 45. Phase IV b eg an w hen the elbow angle was 45 and e nded w hen the elbow re ached its greatest degree of flexion. These phases w ere used to discuss a n d describe th e m echanics of the biceps curl throughout this chapter. H om ogeneity of V ariance F-ratios w ere c alculated to determ ine if hom ogeneity, with respect to variance, existed b etw e en the five conditions. extrem e conditions w ere com pared. In this particular study only variances for the More specifically, the 60% RM condition was c o m p a re d to the 70% RM, 80% RM, 90% RM, and 100% RM conditions. Only the comparisons in which there was an absence of hom ogeneity w ere addressed. The hom ogeneity of variance comparisons (see Table 1 ) indicated the following: 1. An absence of hom ogeneity, F=3.34, existed b etw e en Condition 1 and Condition 2 in the shoulder a n g le a t 135 elbow flexion (F(9,9)=3.16, jo<.05). 2. An absence of hom ogeneity, F=3.65, existed b etw e en Condition 1 and Condition 2 in the trunk ang le a t 135 elbow flexion (F(9,9)=3.16, <.05). 3. An absence of hom ogeneity, F=4.84, existed b e tw e e n Condition 1 and Condition 2 in the bo d y ang le a t 135 elbow flexion (F(9,9)=3.16, <.05). 4. An absence of hom ogeneity, =4.0, existed b e tw e e n Condition 1 and Condition 3 in the b ody ang le a t 135 elbow flexion (F(9,9)=3.16, <.05). 5. An absence of hom ogeneity, F=3.72, existed b e tw e e n Condition 1 and Condition 4 in the trunk ang le a t the initiation of m ovem ent (F(9,9)=3.16, jo<.05). 6. An absence of hom ogeneity, F=6.6, existed b e tw e e n Condition 1 and Condition 4 in the trunk ang le a t 90 elbow flexion ( (9,9)=3.16, <.05). 7. An ab sen ce of hom ogeneity, F=4.12, existed b e tw e e n Condition 1 an d

37 Condition 4 in the body angle a t 135 elbow flexion (F(9,9)=3.16, <.05). 8. An absence of hom ogeneity, F=6.66, existed b etw e en Condition 1 and Condition 4 in the body angle a t 90 elbow flexion (F(9,9)=3.16, <.05). 9. An absence of hom ogeneity, F=4.08, existed b etw e en Condition 1 and Condition 5 in the trunk ang le a t 135 elbow flexion(f(9,9)=3.16, <.05). 10. An absence of hom ogeneity, F=7.95, existed betw een Condition 1 and Condition 5 in the trunk angle a t 90 elbow flexion (F(9,9)=3.16, <.05). 11. An absence of hom ogeneity, F=8.8, existed b etw e en Condition 1 and Condition 5 in the trunk ang le a t 45 elbow flexion (F(9,9)=3.16, <.05). 12. An absence of hom ogeneity, F=5.13, existed betw een Condition 1 and Condition 5 in the body angle a t 45 flexion (F(9,9)=3.16, <.05). 13. An absence of hom ogeneity, F=4.19, existed betw een Condition 1 and Condition 5 in the body angle a t the com pletion of m ovem ent (F(9.9)=3.16. <.05). 14. An absence of hom ogeneity, F=4.43, existed betw een Condition 1 and Condition 2 in the knee an g le a t 45 elbow flexion (F(9,9)=3.16, <.05). Shoulder Angle Three landmarks w ere used to calculate the shoulder angle, two of these landmarks w ere endpoints a n d one was the vertex. The right elbow was the first endpoint (P I), the right shoulder was the vertex (V), and the horizontal was the second endpoint (P2). For this angle, 90 represented the anatom ical position. Angular values g reater than 90 indicated extension, while values less than 90 indicated flexion. Based upon the g en erated shoulder angle d a ta the subjects w ere grouped with respect to similar m ovem ent patterns that w ere m aintained across all of the conditions. For the shoulder angle three distinct m ovem ent patterns w ere identified. Subjects 1, 7, and 9 comprised one of these three groups. In Phase I and Phase II the

38 Table 1 Summary Table for Hom ogeneity of V ariance Joint Initiation Completion Condition 1 VS. Condition 2 Shoulder * Trunk Body * Knee Condition 1 VS. Condition 3 Shoulder Trunk Body Knee Condition 1 VS. Condition 4 Shoulder , Trunk 3.72* Body * 6.66* Knee Condition 1 VS. Condition 5 Shoulder Trunk * Body * Knee * F(9,9) = jd <.05 shoulder extended, as indicated by the progressive increase in the shoulder angle values. In Phase III and Phase IV the direction of shoulder m ovem ent c h a n g ed and th e shoulder flexed, evid enced by the decrease in shoulder angle values. In Phase III there was a dram atic decrease in the shoulder angle, while the decrease in Phase IV